Mariner 1

NASA's first attempt at Venus was destroyed by the range safety officer about five minutes after launch on 22 July 1962. Newspapers blamed a missing hyphen; most later accounts describe a missing overbar in the handwritten guidance equations, so the software used unsmoothed velocity data and overreacted once a hardware fault came into play. Accounts of the exact character still differ. The lesson holds either way. Every transcription step between a specification and code is a place where meaning can silently vanish, and a defect that only bites when another component fails will slip straight past ordinary testing. Arthur C. Clarke called it the most expensive hyphen in history.